This invention relates to the field of radiant energy systems for detecting and assessing distant objects.
Previous uses of laser radar to sense target vibrations have employed continuous wave (CW) lasers. Such CW lasers, however, provide no range resolved information so that it is difficult if not impossible in such systems to separate frequency information arising from vibrations of the sensor platform from those of interest of the target.
Previous attempts to segregate target and sensor platform vibrations have therefore employed gyroscopic or inertial reference based sensors to attempt a determination of the motion of the platform. However, such sensors are cumbersome and difficult to use, and are limited in frequency and spatial response. Moreover, and also platform motions too small to be sensed by these sensors may in fact contribute significantly to the spectrum noise of the sensed target.
The recent emergence of practical optical radars or laser radars (i.e. ladar) systems which operate in the near-infrared region of wavelength, such as the two micrometer laser based systems, has however made a different and more practical approach to the moving platform based assessment of a vibrating target possible. Such a system is the subject of the present patent document.